1. Field of the Invention
The present invention is directed to an implantable electrode device, of the type intended for connection to a medical apparatus for delivering electrical energy, such as electrical pulses, to living tissue.
2. Description of the Prior Art
Implantable electrode devices are generally known in the art for connection to a medical apparatus to deliver electrical impulses in vivo to tissue. Such known devices include an electrode catheter which contains a lead, one end of which is equipped with a connection contact (jack) for inserting the lead into a pulse generator, the other end of the catheter and lead being connected to a flat, flexible electrode carrier consisting of electrically insulating material, on which at least one electrode conductor is arranged in a predetermined pattern, the conductor being electrically conducted to the lead. A portion of the conductor is exposed to form an active electrode surface.
Such an electrode device is disclosed in U.S. Pat. No. 4,817,634. In this known electrode device, the insulating electrode carrier has a groove therein which follows a predetermined pattern in which an electrode conductor is placed. The electrode conductor is coiled around an insulating core, and is coupled to a contact clamp for electrically coupling an electrode lead thereto, contained in an electrode catheter. The electrode device is designed to be sutured to the heart of a patient in order to transmit defibrillation pulses to the heart from an implanted defibrillator.
During implantation of this known electrode device in a patient, the device is placed so that it surrounds a large portion of the heart, thereby substantially electrically insulating the heart from its surrounding tissue. As a result, any external defibrillation pulse subsequently delivered to the patient could be wholly or partially ineffective, because the insulating electrode carrier would prevent such externally-applied electrical impulses from reaching the heart. In addition, this known electrode device presents an obstacle to any subsequent heart surgery, for example, for removal of damaged heart tissue.
Another known electrode device is disclosed in U.S. Pat. No. 4,567,900 wherein the electrode is formed by a resilient conductor curved in such a manner as to exhibit a ring-shaped electrode contour. Thin, flexible, conductor strips are arranged in a grid pattern within the ring-shaped contour to form the electrode surface. The conductor can be compressed into a narrow, elongated form in which it can be placed inside an introducer catheter and thereby advanced to the heart. The electrode is completely uninsulated and is designed for loose placement between the pericardium and the epicardium. If the electrode were placed at any other location, the uninsulated electrode could damage adjacent tissue. There is no discussion in this patent as to how the electrode would be prevented from shifting position before it becomes embedded in cardiac tissue by tissue ingrowth.